The present invention relates to improvements in metal halogen battery systems. More particularly the invention relates to a new multiple outlet nozzle means for use in connection with the hydrate former associated with the hydrate store of the battery system.
The electrical energy storage systems of the type referred to herein (e.g., a zinc chlorine battery system or other metal-halogen battery system) utilize a halogen hydrate as the source of a halogen component for reduction at a normally positive electrode, and an oxidizable metal adapted to become oxidized at a normally negative electrode during the normal discharge of the storage system. An aqueous electrolyte is employed for replenishing the supply of the halogen components as it becomes reduced at the positive electrode. The electrolyte contains the dissolved ions of the oxidized metal and the reduced halogen and is circulated between the electrode area and a storage area containing halogen hydrate, which progressively decomposes during a normal discharge of the electrical energy system, liberating additional elemental halogen to be consumed at the positive electrode.
The state of the art in electrical energy storage systems or battery systems of this type is described in the following cited references owned by the same assignee as the present invention, such as Symons U.S. Pat. No. 3,713,888; Symons U.S. Pat. No. 3,809,578 entitled "Process for Forming and Storing Halogen Hydrate in a Battery"; and Bjorkman U.S. Pat. No. 3,814,630 entitled "Filter/Store For Electric Energy Storage Device"; and, in commonly assigned copending Bjorkman U.S. patent application Ser. No. 368,892, filed Apr. 16, 1982, entitled "Multiple Stage Multiple Filter Hydrate Store".
The specific teachings of the aforementioned cited references are incorporated herein by reference. The new multiple outlet nozzle disclosed herein is particularly useful for application in a battery system of the type described in the copending application referred to immediately above. However, it also has wide application for use in numerous metal halogen battery systems.
The basic operation of a zinc chloride battery system is as follows. In charge, an electrolyte pump delivers aqueous electrolyte to pockets between pairs of porous graphite-chlorine electrodes in a battery stack comprised of a plurality of cells. The electrolyte passes through the porous chlorine electrodes into a chamber between opposite polarity electrodes, flows up between the electrodes, then flows back into the battery sump. Chlorine gas liberated from porous graphite electrode substrates is pumped by a gear pump, otherwise referred to as the gas pump, and before entering the gas pump, the chlorine is mixed with electrolyte chilled by a chiller unit. The chlorine and chilled electrolyte are mixed in the gear pump, chlorine hydrate forms, and the chlorine hydrate-electrolyte mixture is deposited in the store. In discharge, chlorine is liberated from hydrate by decomposition of chlorine hydrate in the store by injection of warm electrolyte from the sump. On development of the required chlorine gas pressure in the store, the chlorine is injected and mixed with and dissolved in the electrolyte, which is then fed to the porous electrodes in the battery stack. The battery stack is then discharged, wherein the electrode dissolution of zinc occurs at the zinc electrode, reduction of the dissolved chlorine occurs at the chlorine electrode, power is available from the battery terminals, and zinc chloride is formed in the electrolyte by reaction of zinc and chlorine to form zinc chloride.
The state of the prior art has been to use a single nozzle outlet from the gear pump used to form chlorine hydrate in a zinc-chlorine battery system. Chlorine gas and cold liquid electrolyte were mixed in the pump causing solid particulate chlorine hydrate to be formed. The mixture of electrolyte, particulate hydrate and unreacted gas was expelled into a tank filter (container lined with filter cloth) called the "Hydrate Store". In many battery systems, however, as the battery charge progressed, the particulate hydrate gradually filled the available space with a loosely packed bed of particulate material. The filtration process began to "back up" into the single nozzle outlet where the liquid velocities were much higher than in the relatively large volume of the tank. The result in many instances has been premature, rapid buildup of high pressures in the pump outlet, even though the store volume was not fully packed with particulate hydrate. If the gear pump were turned off for a period of time, the nozzle would often clear, and operation could be resumed. However, as can be appreciated a shut-down of the pump is time consuming and very detrimental to efficient continuous running of the battery.
Accordingly it is a primary object of this invention to provide a novel metal halogen battery system which includes an improved hydrate former which minimizes hydrate plugging.
Other objects, features and advantages of the invention will become apparent from the description herein, from the drawings, and from the appended claims.